如何从 Firestore 渲染数据以响应本机组件？

Question

I have been trying to render information from my firebase to a react native component. I started by console logging what I have done, the data is being fetched completely fine:

displayAllPlayers(){
dbh.collection('Players').get()
.then(querySnapshot => {
    querySnapshot.forEach(doc => {
        console.log(doc.data().First, doc.data().Last)
    })
})}

I then tried to add this information to my component as follows:

displayAllPlayers(){
dbh.collection('Players').get()
.then(querySnapshot => {
    querySnapshot.forEach(doc => {
        <Player key={doc.data().First} fName={doc.data().First} lName={doc.data().Last} />
    })
})
}
render() { 
    const myPlayers = this.displayAllPlayers()
} 
return(
    {myPlayers}
)

Answer 1

• You should return the JSX inside the render function.

• displayAllPlayers isn't returning anything.

• In this snippet

   querySnapshot.forEach(doc => { <Player key={doc.data().First} fName={doc.data().First} lName={doc.data().Last} /> })

  you're not returning anything inside the callback passed to forEach even if you do, it doesn't work because forEach doesn't return an array. You can use map here.

• Maintain a state in the component and update it once you get the data. Use this state for rendering the array of JSX elements.

Answer 2

It's always suggested to create a different helpers file.

Create a firebase-helpers.js file which has an function to convert snapshot to array.

// FILENAME - firebase-helpers.js
export const snapshotToArray = (snapshot) => {
  let returnArr = [];

  snapshot.forEach((childSnapshot) => {
    let item = childSnapshot.data();

    returnArr.push(item);
  });

  return returnArr;
};

Now in your screen, import this file

import { snapshotToArray } from "../helpers/firebaseHelpers";

Then, convert snapshot of Players to array

const playersSnapshot = dbh.collection('Players').get();
const playersArray = snapshotToArray(playersSnapshot);
this.setState({ players : playersArray });

Now in state you have an array players. To display content of Players, you can use in your render function as -

<FlatList
   data={this.state.players}
   renderItem={({ item }, index) => this.playerDisplay(item, index)}
   keyExtractor={(item, index) => index.toString()}
/>

You can then have a function to return details of players as -

playerDisplay = (item, index) => {
  return(
    <View>
          <Text>
                Player {index} - {item.First} {item.Last}
          </Text>
    </View>
  );
}

I hope it works fine.